This invention relates to a display method and apparatus for navigation system, and more particularly, to a display method and apparatus for a navigation system which is capable of displaying a guidance map showing appropriate number of upcoming and subsequent turns on the route to the destination with an appropriate display size.
A vehicle navigation system performs vehicle travel guidance for enabling a driver to easily drive the vehicle to a selected destination. Typically, a navigation system displays a direction of the next turn in a highlighted route format on the guidance map. This invention is directed to a display method and apparatus for displaying directions of turns when there are two or more turns in succession within a short distance on the route to the destination.
First, basic technology of a navigation system is briefly described here. Such a navigation system detects the position of the vehicle, reads out map data pertaining to an area at the vehicle current position from a data storage medium, for example, a CD-ROM (compact disk read-only memory) or a DVD (digital versatile disc), and displays a map image on a monitor screen (display) while superimposing a mark representing the current location of the vehicle on the map image.
The vehicle position is determined by a self-contained navigation sensors (e.g. Ea distance traveled sensor and a bearing sensor) mounted in the vehicle or by a global positioning system (GPS) including an artificial satellite (satellite navigation). The satellite enables absolute position detection and higher position accuracy than the self-contained navigation sensors. However, the satellite navigation involves problem of position detection failure such as in a tunnel or a building where the satellite radio signals are obstructed. Therefore, recent navigation systems utilize both self-contained navigation and satellite navigation to achieve improved performances.
As the present position of the vehicle changes with the travel of the vehicle, the vehicle current position mark in the map image on the screen is changed accordingly. Alternatively, the map is scrolled while the vehicle current position mark is fixed at a predetermined position, for example, at the center of the image. In either method, the navigation system enables the driver to recognize the map information of the area at the vehicle position at a glance.
When a destination is not set, such a navigation system functions as a locator map which indicates the current location of the vehicle on a map image. When the destination is set, the navigation system starts a route guidance function for setting a guided route from the starting point to the destination. Typically, the route guidance function performs an intersection guidance process in which a monitor screen displays an enlarged intersection diagram and the direction in which the vehicle is to travel while displaying the guide route on a map. When a destination is input, a CPU in the navigation system determines a most suitable guided route from the current vehicle position to the destination and successively stores nodes (expressed in longitude and latitude) constituting the guided route in a memory.
During actual traveling, the node series stored in the memory is searched for a portion of the guided route to be displayed in a map display area of the monitor screen, and the portion of the guided route is highlighted so as to be discriminable from other routes. When the vehicle is within a predetermined distance of an intersection it is approaching, an intersection guidance diagram (an enlarged or highlighted intersection diagram with an arrow indicating the direction in which the vehicle is to turn at the intersection) is displayed to inform a driver of the desired one of roads or directions selectable at the intersection.
FIG. 1A shows an example of a locator map display containing a vehicle current position mark VCP on a map image 21. Typically, a navigation system shows the street on which the vehicle is running in the map image 21 and a name of the street such as xe2x80x9cW 190TH STxe2x80x9d in an information box 23 on the monitor screen. Other information such as a north pointer NP, a map scale and a current time may also be illustrated on the display screen. In this manner, the locator map display shows the current position of the vehicle on the map image, however, it does not perform the route guidance function because the destination is not set in the navigation system.
FIG. 1B shows an example of route guidance display which performs the route guidance function. The route guidance display is activated after specifying the destination. In addition to the map image 21 similar to the locator map of FIG. 1A, this example further shows an arrow indicating the direction (left) in which the vehicle is to turn at the intersection in a guidance information box 22 at the top of the screen. The guidance information box 22 also shows a name of the street xe2x80x9cPRAIRIE AVExe2x80x9d which intersects with the current street xe2x80x9cW 190TH STxe2x80x9d and a distance to the intersection. Thus, the navigation system indicates that the vehicle should make a left turn at the intersection with xe2x80x9cPRAIRIE AVExe2x80x9d.
Typically, the current street xe2x80x9cW 190TH STxe2x80x9d and the left side of the street xe2x80x9cPRAIRIE AVExe2x80x9d will be highlighted in the map image 21. Further, such route guidance is accompanied by voice instructions. If the direction of travel in the next intersection is left, the navigation system gives spoken guidance such as xe2x80x9cturn left at the next intersectionxe2x80x9d. In this example, an information box 24 at the bottom of the display screen includes information regarding the remaining distance to the final destination and an estimated time to reach the final destination.
In order to be guided by the route guidance mode such as shown in FIG. 1B, a destination must be specified in the navigation system so that the system can find one or more routes to get to the destination. FIGS. 2A-2F show examples of display shown on the monitor screen during the operation of inputting the destination.
By operating a menu key, a main menu 25 such as shown in FIG. 2A is displayed on the navigation system and a menu item xe2x80x9cDestinationxe2x80x9d is selected from the main menu. This allows the navigation system to display a xe2x80x9cEnter Destination byxe2x80x9d menu 27 as shown in FIG. 2B for specifying an input method for selecting the destination. The xe2x80x9cEnter Destination byxe2x80x9d menu 27 lists various methods for selecting the destination including xe2x80x9cAddressxe2x80x9d for specifying the city and address of the destination, xe2x80x9cIntersectionxe2x80x9d for specifying the names of two streets in the city which intersect with one another, and xe2x80x9cPoint of Interestxe2x80x9d for selecting the programmed destination based on the name, category or telephone number.
Other methods in the xe2x80x9cEnter Destination byxe2x80x9d menu 27 include xe2x80x9cRecent Routexe2x80x9d for specifying the destination based on the recent destinations saved in the navigation system, xe2x80x9cAddress Bookxe2x80x9d for selecting the address of the destination out of the addresses stored in the system, and xe2x80x9cMap Cursorxe2x80x9d for specifying the destination by pointing a cursor to the destination on the map. For example, the information in the address book is formed of a list of names and addresses of the places that the driver frequently visits.
When selecting, for example, the xe2x80x9cPoint of Interestxe2x80x9d in FIG. 2B, the navigation system displays a xe2x80x9cCategory Listxe2x80x9d menu 28 such as shown in FIG. 2C. The xe2x80x9cCategory Listxe2x80x9d menu 28 contains various different categories such as xe2x80x9cBankxe2x80x9d, xe2x80x9cRestaurantxe2x80x9d, xe2x80x9cHotelxe2x80x9d, xe2x80x9cShoppingxe2x80x9d and others. Supposing the category xe2x80x9cShoppingxe2x80x9d is selected, the navigation system displays xe2x80x9cName Listxe2x80x9d such as shown in FIGS. 2D and 2E. The xe2x80x9cName Listxe2x80x9d shows names of shops and shopping malls sorted by, for example, distance from the vehicle. In an address information box 31 on the display, the address and phone number of the highlighted name in the list 33 will be displayed. The address information box 31 may also show the distance to the highlighted shop. Typically, the navigation system stores several tens or hundreds of names of shops within predetermined distances and displays several shops per page of display screen, and a user may scroll the display screen to see other names of shops in the name list 36 such as shown in FIG. 2E.
When the destination is not prestored in the navigation system, a user can input the destination by selecting, for example, the xe2x80x9cAddressxe2x80x9d method or xe2x80x9cIntersectionxe2x80x9d method in the xe2x80x9cEnter Destination byxe2x80x9d menu 27 of FIG. 2B. Then, the navigation system displays an xe2x80x9cEnter Street Namexe2x80x9d shown in FIG. 2F for inputting the city and address in an address input box 37 by means of a key board (keypad) 38 displayed on the monitor screen.
After inputting the destination, the navigation system determines a route to the destination based on, for example, the shortest way to reach the destination, the route preferring freeways to surface roads or the route without using toll road, and the like. Thus, the navigation system moves to the route guidance display such as shown in FIG. 1B which performs the route guidance.
In the route guidance, the direction of next turn is illustrated by arrow (arrow guidance) or highlighted route (map guidance) as shown in FIG. 1B. Such route guidance by the navigation system is also given by voice instruction. When there is a second turn relatively close to the first turn, the navigation system shows the first and second turns on the display depending on predetermined conditions.
Such an example of displaying the first turn or both of the first and second turns is shown in FIGS. 3A-3B and 4A-4B. This conventional technology is disclosed in the U.S. Pat. No. 5,739,772 which is directed to the arrow guidance. FIGS. 3A and 3B show a case where the distance D1 between the first turn P1 and the second turn P2 is smaller than a predetermined amount. In contrast, FIGS. 4A and 4B show a case where the distance D2 between the first turn Q1 and the second turn Q2 is larger than the predetermined amount.
When the second turn is near the first turn, as in the case of FIG. 3A, the navigation system detects that the distance between the first turn P1 and the second turn P2 is smaller than the predetermined amount. Then the navigation system displays two arrows respectively indicating the directions of the first turn P1 and the second turns P2 on the screen in a partially overlapped manner in FIG. 3B.
When the second turn is away from the first turn, as in the case of FIG. 4A, the navigation system detects that the distance between the first turn P1 and the second turn P2 is larger than the predetermined amount. Then the navigation system displays only one arrow indicating the direction of the first turn P1.
In this conventional technology, only one or two arrows will be displayed on the screen. Thus, it is not possible to provide a driver sufficient information or a route image regarding the subsequent turns, such as how soon the subsequent turn comes or whether there is a further turn immediately after the subsequent turn, etc. Therefore, there is a need in the navigation system to illustrate an optimum number of turns on the guidance map with an optimum size of the map so that the driver is able to grasp the upcoming turns and succeeding turns at a glance.
It is, therefore, an object of the present invention to provide a display method and apparatus for navigation system which enables a user to easily and quickly grasp the turn maneuvers and directions in the map guidance mode with optimum window sizing.
The navigation system is designed to enable a user to quickly observe the two or more turn maneuvers on the map image to fully prepare for the turns coming in succession. The navigation system applies various test conditions and determines optimum number of turns to be displayed and enlarges the guidance map by removing the unnecessary turns from displaying on the screen. Not all of the test conditions may necessarily be used but various combinations of test conditions can be advantageously used in the navigation system.
More specifically, the method of the present invention includes steps of: displaying a guidance map for guiding a user to a destination by indicating a maneuver point on the route and a direction of turn at the maneuver point; detecting a plurality of maneuver points in succession on the route to the destination and applying at least one test condition to the maneuver points based on geometry of the maneuver points; adjusting a number of maneuver points to be displayed on the guidance map; and enlarging a size of the guidance map while including the adjusted number of maneuver points in the guidance map.
The step of enlarging the guidance map includes a step of maximizing the size of the guidance map while sufficiently including all of the adjusted number of maneuver points. The step of adjusting the number of maneuver points includes a step of including a maneuver point which forms a street shorter than a predetermined length defined by the test condition in the guidance map and a step of removing a maneuver point which forms a street longer than the predetermined length defined by the test condition from the guidance map.
The test condition includes a test condition (1) which determines L(n, n+1)xe2x89xa6Lmax, where L(n, n+1) is a drive length along a street between two adjacent maneuver points Pn and Pn+1, and Lmax is a maximum allowable drive length of the a street between the two adjacent maneuver points.
The test condition includes a test condition (2) which determines L(n, n+1)xe2x89xa6KDD(1, 2), where L(n, n+1) is a drive length along a street between two adjacent maneuver points Pn and Pn+1, D(1, 2) is a straight-line length between a first maneuver point P1 and a second maneuver point P2, and KD is a relative factor for determining maximum allowable straight-line maneuvers. This test condition can be modified to D(n, n+1)xe2x89xa6KDDD(1, 2), where KDD is a relative factor equivalent to KD above but is applicable to the straight-line length between points Pn and Pn+1 instead of the drive length between the two maneuver points.
The test condition includes a test condition (3) which determines L(n, n+1)xe2x89xa6KLDD(n, n+1), where L(n, n+1) is a drive length along the street between two adjacent maneuver points Pn and Pn+1, D(n, n+1) is a straight-line length between the two adjacent maneuver points Pn and Pn+1, and KLD is a relative factor for determining a maximum drive length with respect to the straight-line distance.
The test condition includes a test condition (4) which determines D(1, n+1)xe2x89xa6Dmax, where D(1, n+1) is a straight-line distance between a first maneuver point P1 and a farthest maneuver point Pn+1, and Dmax is a maximum allowable distance between the first maneuver point P1 and farthest maneuver point Pn+1. Further, the test condition includes a test condition (5) which determines mxe2x89xa6Mmax, where m is a number of maneuvers in succession, and Mmax is a maximum allowable number of maneuver points that can simultaneously appear on guidance map.
Another aspect of the present invention is a display apparatus for a vehicle navigation system. The display apparatus is configured by various means for achieving the display methods described above which applies the various test conditions to the series of turns on the route to the destination and adjusts the number of maneuver points and produces the enlarged guidance map.
According to the present invention, the vehicle navigation system enables the user to easily grasp the consecutive turns and their directions on the route to the destination. The driver can check and grasp the maneuver points at a glance and fully prepare for the next turn such as by changing lanes. Accordingly, the driver can travel to the destination comfortably and with confidence.